In November and December, sales are thought to have risen 28% year on year to more than $15.5bn (£8bn), excluding auctions and travel sales, according to research firm ComScore.

This contrasts with an at best flat picture for mainstream US retailers. Wal-Mart, the world's biggest and a crucial indicator of consumer health in the US, said seasonal sales growth would probably be in the 1-3% range - its lowest monthly growth forecast since early 2003.

Nonetheless, Wal-Mart's figures are still on course with expectations, and were enough to stave off complete gloom among retail analysts.